The impact of a population-based screening program on income and immigration-related disparities in colorectal cancer screening

A population-based program promoting the Fecal Occult Blood Test (FOBT) for colorectal cancer screening was introduced in 2008 in Ontario, Canada, where opportunistic screening with colonoscopy had been increasing in frequency. We evaluated the impact of the program on income and immigration-related disparities in screening. We used linked administrative data to calculate colorectal cancer screening rates for eligible Ontarians in each year between 2001/02 (n=2,852,619) and 2013/14 (n=4,139,304). We quantified disparities using an "inequality ratio" of screening rates in the most disadvantaged group relative to the most advantaged group. We performed segmented logistic regression analyses stratified by screening modality and adjusted for age, sex, rurality, co-morbidity, and morbidity. Between 2001/02 and 2013/14, the income and immigration inequality ratios narrowed from 0.74 to 0.80 and 0.55 to 0.69, respectively. Before the screening program, the income inequality ratio was widening by 1% per year (95% CI 1% to 1%); in the year it was introduced, it narrowed by 4% (95% CI 2% to 7%) and in the years following, it remained stable [0% change (95% CI 1% decrease to 0% decrease) per year]. Results were similar for immigration-related disparities. After program introduction, disparities in receiving FOBT were narrowing at a faster rate while disparities in receiving colonoscopy were widening at a slower rate. In summary, introduction of a population-based screening program promoting FOBT for colorectal cancer was associated with only modest improvements in immigration and income-related disparities. Disparities seemed to be driven by a higher uptake of colonoscopy among more advantaged groups.